1. Field of the Invention
The present invention relates to a gas turbine combustor.
2. Description of the Related Art
In industrial gas turbine combustors, a need exists for reduction in environmental loads and reduction in the amount of nitrogen oxide (NOx) emissions produced from combustion has become one of the major challenges that the industry must face in recent years. The amount of NOx emissions can be reduced by preventing a local high-temperature zone from occurring in the gas turbine combustor. One possible solution is, specifically, to mix fuel and air before the combustion to thereby burn the mixture at a fuel-air mixture ratio lower than a stoichiometric mixture ratio. Thus, increasing the amount of combustion air to thereby reduce the mixture ratio is effective in reducing the amount of NOx emissions.
The gas turbine combustor typically includes a mixer that mixes fuel with air to produce a mixture and a combustion chamber that is disposed downstream of the mixer and burns the mixture. A combustion reaction takes place inside the combustion chamber and thus the combustion chamber wall is exposed to combustion gas at high temperature. Known gas turbine combustors incorporate a film cooling structure that causes part of the combustion air to flow as a film of cooling air along the combustion chamber wall surface.
In general, compressed air supplied from a compressor to a combustor is divided into cooling air for cooling the combustion chamber wall and combustion air. As a result, increasing the amount of the combustion chamber wall cooling air results in a decreased amount of combustion air, which makes it difficult to reduce the amount of NOx emissions. A known method (disclosed, for example, in JP-2009-79789-A) enhances cooling efficiency to reduce the amount of cooling air as follows. Specifically, a path through which cooling air is passed is formed in the combustion chamber wall and the method uses both convection cooling achieved by the cooling air passing through the path and film cooling achieved by air that comes out of the path.